<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>自定义函数</title>
		<script>
			function add(a,b=100){
				c= a+b;
				document.write("结果是"+c);
			}
			function add(a,b=100,c=200){
				c= a+b+c;
				document.write("结果是"+c);
			}
			document.write("<h1>按钮的事件</h1>");
		</script>
	</head>
	<body>
		<button type="button" onclick="add(3,6)" >点击执行</button>
	</body>
</html>